The 'best guess' EI for your first trials should be Ilford's ISO numbers: 100 for Delta 100, etc. Then adjust if necessary when you can see the processed negatives.(posted 9240 days ago)The main purpose for pulling developmnent is to adjust contrast rather than EI. So if your subject was very contrasty, pulling the development may be advisable. If you have over-exposed a 'normal' subject by one stop, then pulling the devlopment of Delta films isn't necessary (but may be slightly beneficial).